Elected officials who take free trips without getting clearance are entering very murky ethical grounds, Mayor Bloomberg warned yesterday.

“I think there’s got to be some standards because it’s too obvious a way to curry favor,” the mayor said.

“The potential conflict is great. It’s not that much different from making donations to campaigns and then putting legislation in front of the recipients and asking them to vote or something like that. It’s just another way of trying to influence. It’s a little bit different if it’s a trade group, I suppose. But it’s a slippery slope.”

Bloomberg’s comments came two days after the Conflicts of Interest Board slapped Brooklyn Borough President Marty Markowitz with a $20,000 fine for bringing his wife on official visits to Holland and Turkey in 2009. The two governments picked up both their tabs.